The purpose of this study was to determine whether female American lobsters (Homarus americanus) inhabiting different offshore areas reached sexual maturity at different sizes. We determined the sexual maturity of 734 lobsters captured in three different offshore locations (North: Georges Bank and offshore Gulf of Maine; Middle: southern New England shelf and slope and; South: offshore Rhode Island to New Jersey) using a combination of methods including abdominal width : carapace length ratios, cement gland examination, and ovarian staging. Lobsters that experienced the most degree-days > 8°C (dd) reached sexual maturity at smaller sizes. The size at which 50 percent of the lobsters were mature was 79 mm CL for the South (annual dd = 808), 82 mm CL for the Middle (999 dd), and 92 mm CL for the North (234 dd). This regional difference in size at maturity was also manifested in the average size, and range of sizes, of berried females captured in each location. These data will likely be of use when developing appropriate regulations for managing the offshore fishery.